Expandable medical device delivery system and method

ABSTRACT

A delivery system and method are provided for accurately locating, orienting, and implanting expandable tissue supporting devices at a lumen junction or bifurcation in a body lumen. For example, the system may be used to deliver a tissue supporting device to a bifurcated artery such that, on expansion, the tissue supporting device provides side ports of a specific size and geometry to accommodate bifurcations in the artery. The delivery system is capable of accurately orienting these side ports both radially and longitudinally with respect to branch lumen openings of the artery. The delivery system achieves orientation by utilizing a guide member which is positioned to extend from the side port feature of the tissue supporting device. The guide member is tracked along a guidewire which extends into the branch lumen, ultimately orienting the side port of the tissue supporting device properly at the branch lumen opening. After expansion of the tissue supporting device, the guide member-drops out of the enlarged side port and is withdrawn.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a delivery system and method fordelivering tissue supporting medical devices, and more particularly to asystem and method for implanting expandable, non-removable devices atthe junction of two or more bodily lumens in a living animal or human tosupport the organs and maintain patency.

2. Summary of the Related Art

In the past, permanent or biodegradable devices have been developed forimplantation within a body passageway to maintain patency of thepassageway. These devices are typically introduced percutaneously, andtransported transluminally until positioned at a desired location withinthe body passageway. The devices are then expanded either mechanically,such as by the expansion of a mandrel or balloon positioned inside thedevice, or expand themselves by releasing stored energy upon actuationwithin the body. Once expanded within the lumen, these devices, calledstents, become encapsulated within the body tissue and remain apermanent implant.

Frequently, the area to be supported by such devices is located at ornear the junction of two or more lumens, called a bifurcation. Incoronary angioplasty procedures, for example, it has been estimated that15% to 20% of cases involve reinforcing the area at the junction of twoarteries. Conventional stent implantation at such a junction results inat least partial blockage of the branch artery, affecting blood flow andimpeding access to the branch artery for further angioplasty procedures.

Known techniques for treating bifurcations generally deliver a meshtissue supporting device into the artery and position the device overthe bifurcation. According to the known methods, a surgeon then attemptsto create one or more branch lumen access holes by inserting a balloonthrough the sidewall of the mesh device, and then inflating the balloonto simply push the local features of the mesh aside. These techniquesare inherently random in nature: the exact point of expansion in thedevice lattice cannot be predicted, and the device may or may not expandsatisfactorily at that point. Tissue support provided by these knowntechniques for treating bifurcated arteries is similarly unpredictable.In addition, the effectiveness of such procedures is limited becausemany mesh devices are unable to accommodate such expansion at randomlocations in the device structure. Further, prior art tissue supportingdevice delivery systems are unable to accurately position specificdevice features over the branch artery opening.

Prior art tissue supporting devices for bifurcations generally have notattempted to orient the device radially at the branch lumen opening.Rather, these stents included a section along their axis or at one endat which several enlarged expansion cells were distributed uniformlyaround the stent circumference. The presumption was that after stentinsertion, one or the other of these cells would be oriented closelyenough with the branch lumen opening that the subsequent proceduresmentioned above would clear the opening. One example of such a device isthe Jostent® bifurcation stent design which has an 8 cellcircumferential construction over half the stent length and either 2 or3 rows of larger cells which can be post-dilated to allow access forplacement in a bifurcated vessel. One problem with this technique isthat the resulting density of stent features at the area of thebifurcation is so low that there is very little stent strength aroundthe rest of the circumference of the main artery for tissue support.Thus, the lumen junction area, which requires the greatest tissuesupport, actually gets the lowest support. For the same reason, suchtissue supporting devices also provide a low ratio of tissue coverage(metal-to-tissue area ratio) in the junction area. Low metal coverageand the resulting tissue prolapse are associated with higher restenosisrates.

Another method for deploying a stent in a bifurcating vessel isdescribed in International Application WO98/19628. According to thismethod, a main stent having a substantially circular side opening and aflared stent having a flared end are used together to treat abifurcating vessel in a two step process. In a first step, the mainstent is positioned using an inflatable balloon catheter in the interiorof the main stent and a stabilizing catheter extending through the sideopening of the stent. The stabilizing catheter is used to place the sideopening in the main stent at the opening to the branch vessel. The mainstent is then expanded and the flared stent is inserted through the sideopening into the vessel bifurcation. One drawback of this method is thedifficulty in positioning the side opening of the main stent at a properlongitudinal and radial position at the vessel bifurcation. Anotherdrawback of this system is the flared stent which is difficult to formand position, and may tend to protrude into the blood stream causingthrombosis.

In view of the drawbacks of the prior art-bifurcated tissue-supportingsystems, it would be advantageous to have a delivery system capable ofaccurately locating a side port feature of a tissue supporting device ata branch lumen opening, in both the longitudinal and radial directions.

It would further be advantageous if the same delivery system could alsobe used to accurately install and orient a branch lumen second tissuesupporting device.

SUMMARY OF THE INVENTION

The invention includes expandable tissue supporting devices for use atlumen junctions or bifurcations, and a delivery system and method foraccurately. locating, orienting, and implanting the tissue supportingdevices at the lumen junction or bifurcation.

In accordance with one aspect of the present invention, a system isdescribed for delivery of a tissue supporting device to a bifurcatedbody lumen. The system includes a catheter with an inflatable balloonconfigured to deliver an expandable tissue supporting device to thelumen, a guide member received on a side of the balloon and connected tothe catheter, and a branch lumen guidewire extending along an exteriorof the balloon and longitudinally slidable in the guide member.

In accordance with another aspect of the invention, a guide member isdescribed for use in delivery of a tissue supporting device to abifurcated body lumen in a desired longitudinal and radial position. Theguide member includes a guide loop for receiving a guidewire, means forsecuring the guide loop to a catheter, and at least one tab extendingfrom the guide loop for holding the guide loop in position in a sidehole of a tissue supporting device to be delivered.

In accordance with a further aspect of the invention, a method ofdelivering of a tissue supporting device to a bifurcated body lumenincludes the steps of:

-   -   providing an expandable tissue supporting device in an        unexpanded configuration, the tissue supporting device having a        side hole;    -   positioning a guide member in the side hole;    -   positioning a side branch guidewire in a body lumen with a        distal end of the side branch guidewire extending into a        side-branch of a bifurcation;    -   delivering the tissue supporting device into the body lumen by        tracking the guide member along the side branch guidewire;    -   positioning the tissue supporting device with the side hole        aligned radially and longitudinally with an opening of the side        branch; and    -   expanding the tissue supporting device.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be described in greater detail with reference tothe preferred embodiments illustrated in the accompanying drawings, inwhich like elements bear like reference numerals, and wherein:

FIG. 1 is a perspective view of a guide member in accordance with thepresent invention;

FIG. 2 a is a side view of an unexpanded tissue supporting device with aside port, the device has been laid flat for ease of illustration;

FIG. 2 b is a simplified, perspective view of the cylindrical tissuesupporting device of FIG. 2 a;

FIG. 3 is a perspective view of the guide member of FIG. 1 mounted inthe side port of the tissue supporting device of FIGS. 2 a and 2 b;

FIG. 4 is a perspective view of the tissue supporting device of FIGS. 2a and 2 b as it is inserted to a junction of two arteries with a ballooncatheter and two guidewires;

FIG. 5 is a perspective view illustrating a first step of theimplantation sequence: expansion of the distal end of the tissuesupporting device;

FIG. 6 is a perspective view illustrating a second step of theimplantation sequence: withdrawal of the branch lumen guidewire;

FIG. 7 is a perspective view illustrating a third step of theimplantation sequence: expansion of the side port area and proximal endof the tissue supporting device;

FIG. 8 is a perspective view illustrating a fourth step of theimplantation sequence: deflation and withdrawal of the balloon and guideloop;

FIG. 9 is a perspective view of a guide member with an auxiliary guideloop in accordance with the present invention; and

FIG. 10 is a perspective view of the guide member of FIG. 9 mounted in atissue supporting device having two side ports.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention involves a system and method for delivery of a tissuesupporting device to a bifurcated artery such that, on expansion, thetissue supporting device provides side ports of a specific size andgeometry to accommodate bifurcations in the artery. The delivery systemis capable of accurately orienting these side ports both radially andlongitudinally with respect to branch lumen openings of the artery. Thedelivery system achieves orientation by utilizing a guide member 10which is positioned to extend from the side port feature of the tissuesupporting device. The tissue support device is delivered to the arteryon a balloon catheter which is used for expansion of the device. Theguide member 10 is tracked along a side branch guidewire which extendsinto the branch lumen, ultimately orienting the side port of the tissuesupporting device properly at the branch lumen opening. While the tissuesupporting device having the side port is expanded, the guide member 10holds the tissue supporting device in the proper position. Afterexpansion, the guide member 10 drops out of the enlarged side port andis withdrawn with the balloon catheter assembly.

FIG. 1 shows one embodiment of a guide member 10 in accordance with thepresent invention. The device 10 includes a main body 12 of which ispreferably formed as a unitary piece comprising a loop 14, a spacersection 16, and two tabs 18. The inner diameter of the loop 14 is justlarge enough to provide clearance for a guidewire which will passthrough the loop. The loop 14, spacer section 16, and tabs 18 may beintegrally formed from a single piece of tubing. The radius of the tabs18 conforms generally to the inner radius of the unexpanded tissuesupporting device in which the guide loop will be mounted.

The main body 12 of the guide member 10 is attached to a crimping lug 22via a long, flexible tether 20. The tether 20 can be a simple wireattached to the main body 12 and crimping lug 22 at either end, or canbe integrally formed from the same tube as the main body 12 and thecrimping lug 22.

The guide member 10 is preferably made radiopaque by one of severalavailable methods. For example, the wall thickness of the tube may bemade thick enough for good radio opacity. Alternatively, the guide loopmay be made from, plated, or coated with a radiopaque material. This isnot objectionable since the guide member is withdrawn immediately afterthe procedure and does not become a permanent implant. When theradiopaque guide member is crimped into the side port of the tissuesupporting device as described in further detail below, the exactlocation of the side port will be clearly visible on the fluoroscope.

A preferred tissue supporting device for use in the present inventionprovides several capabilities not normally found in conventional stents.The tissue supporting device should provide a side port feature whichwill securely clamp the guide member 10 in the side port when the tissuesupporting device itself is crimped to the catheter balloon. The sideport should expand to some desired shape and release the guide memberwhen the tissue supporting device is expanded. The tissue supportingdevice should also be capable of differential expansion; i.e. differentareas of the device should expand at different balloon pressures, givingthe device the ability to open in a specific sequence.

FIG. 2 a shows a portion of one embodiment of a cylindrical, expandabletissue supporting device 30 which has been laid flat for ease ofillustration. The device 30 of FIG. 2 a is shown in an unexpandedconfiguration and includes a rectangular side hole or port 32. FIG. 2 bshows a simplified cylindrical view of the expandable tissue supportingdevice 30 of FIG. 2 a, with the side port feature 32 shown as arectangular hole in one side. This embodiment of the tissue supportingdevice 30 relies on the use of ductile hinges which interconnect aplurality of struts to achieve the desired performance features. Tissuesupporting devices of the type shown in FIG. 2 a are described infurther detail in U.S. patent application Ser. No. 09/183,555, filedOct. 29, 1998, and in U.S. patent application Ser. No. ______, filed oneven date herewith (attorney docket number 032304-005) which are bothincorporated herein by reference in their entirety.

As shown in FIGS. 2 a and 2 b, the side hole 32 initially takes the formof a rectangular hole in the unexpanded tissue supporting device 30. Theside hole 32 is bordered by six struts 34 that are in turn linked byductile hinges 36. The rectangular side hole 32 fits the profile of theguide loop feature 10 closely, and the excellent crimping properties ofthe ductile hinges allow the hole to close tightly around the guide loopfeature when the tissue supporting device 30 is crimped onto thecatheter balloon. When the tissue supporting device 30 is expanded, suchas by inflation of a balloon, the side hole feature 32 will expand toform an octagonal hole, releasing the guide member 10.

In the tissue supporting device 30 of FIG. 2 a, the ductile hinges 38linking struts 40 on the left or proximal end of the device are widerthan the ductile hinges 42 linking struts 44 on the right or distal endof the device. The width of the ductile hinges is measured in thecircumferential direction of the device 30. As balloon pressure isincreased during expansion of the device 30 the distal end of the devicewill open before the proximal end due to the different configuration ofthe ductile hinges at the two ends of the device. The tissue supportingdevice 30 should be selected so that the device is capable of expansionbeyond a nominal expansion which corresponds to an interior diameter ofthe lumen to be supported. This will ensure that the tissue supportingdevice 30 can be expanded to the desired diameter of the expanded lumenallowing for variations in artery diameters. Allowing for someadditional expansion beyond the nominal expansion of the tissue supportdevice 30 means that some of the struts around the circumference of thedevice will not reach their locking angle when the device has beeninstalled. Accordingly, if the struts 48 all open to their full extentbefore the struts 34 that border the side hole 32, this may result inthe side hole not being fully opened when the tissue supporting deviceis installed. The partially opened side hole may partially block accessto the branch artery. Accordingly, the ductile hinges 36 connecting thestruts 34 that border the side hole 32 are preferably somewhat narrowerthan the ductile hinges 46 of the surrounding struts 48. This willguarantee that the hole feature opens to its final shape before thesurrounding struts 48 reach full expansion.

The present invention will be described with respect to atissue-supporting device having ductile hinges such as the deviceillustrated in FIG. 2 a. However, it should be understood that thesystem and method according to the present invention may also be usedfor delivery of other known tissue supporting devices having side holes.

FIG. 3 illustrates the guide member 10 inserted in the tissue supportingdevice 30 such that the loop 14 projects out through the rectangularside hole 32 and is retained in the hole. The guide member 10 isretained in the side hole 32 by the tabs 16 which are trapped betweenthe tissue supporting device 30 and a balloon catheter assembly.

As shown in FIG. 4, the tissue supporting device 30 and guide member 10are mounted on a catheter balloon 56 and the tissue supporting device 30is crimped down onto the balloon in a known manner. The crimping processcauses the strut elements 34 of the rectangular side hole 32 in thetissue supporting device 30 to close around the guide loop 10, lockingthe guide loop into place in the side hole. The crimping lug 22 of theguide loop 10 is crimped around the catheter 54 just below the proximalend of the balloon assembly, securing the guide member 10 to thecatheter. The catheter and tissue supporting device assembly is nowready for insertion and deployment.

The guide member 10 may take on other configurations as long as theguide member forms a short tube or loop positioned on or secured to theballoon/catheter assembly in such a way that it passes out through theside hole of the tissue supporting device when the device is crimped orotherwise secured on the balloon 56. For example, the guide member maybe formed from a plastic tube and secured directly to the balloon, suchas, by an adhesive.

Prior to insertion of the catheter and tissue supporting deviceassembly, two catheter guidewires are installed by the operator. A firstguidewire 50 follows the main artery 60 as shown in FIG. 4, and a secondguidewire 52 is inserted into the branch artery 62. The catheter 54having the tissue supporting device 30 mounted on the balloon 56 at thedistal end of the catheter is tracked over the main artery guidewire 50.The branch artery guidewire 52 is threaded through the guide loop 12that projects through the top of the tissue supporting device 30. Theassembly is then fed through a catheter guide tube (not shown) to thesite of the bifurcation 68. As the catheter assembly approaches thebifurcation 68, the clevis 64 formed by the tissue supporting device 30and the branch artery guidewire 52 comes to rest against the distal side66 of the branch artery opening. The guide loop 14, and thus the sideport 32 of the tissue supporting device 30 in which it is crimped, isnow located directly under the branch artery opening, and the device isready for deployment. The spacer 16 spaces the guide loop apredetermined distance from the distal edge of the side hole 32 so thatthe side hole will be properly aligned with the opening of thebifurcation 68.

To deploy the tissue supporting device 30, pressure is increased in thecatheter balloon 56 until the distal end 70 of the tissue supportingdevice expands to the lumen diameter of the main artery 60. Thisprocedure locks the tissue supporting device 30 in place in the desiredradial and longitudinal orientation as shown in FIG. 5.

Next, the side branch guidewire 52 is withdrawn from the branch lumen 62and the guide loop 14, and retracted to a position slightly behind theproximal end of the catheter balloon 56 as shown in FIG. 6. The sidebranch guidewire 52 is free to move back and forth longitudinallybecause the proximal end of the tissue supporting device 30 has not beenexpanded. It is desirable to withdraw the side branch guidewire 52temporarily while completing expansion of the proximal end of the tissuesupporting device 30 to avoid pinning the side branch guidewire betweenthe expanded tissue supporting device 30 and the lumen wall. This is thereason that differential expansion capability is beneficial in thetissue supporting device 30.

After withdrawal of the side branch guidewire 52, pressure in thecatheter balloon 56 is increased further, until the side port area andthe proximal end of the tissue supporting device 30 expand to their fullextent. During expansion of the side port area, the spacer 16 and loop14 maintain the longitudinal dimension of the side hole 32 and preventlongitudinal contraction of the side hole during expansion. The mainartery tissue supporting device 30 is now fully deployed with a fullyopen side port 32 a of specific geometry positioned over the branchlumen opening, and a full complement of strut elements deployed aroundthe remainder of the artery opposite the side port to provide goodtissue support as shown in FIG. 7.

The catheter balloon 56 is then deflated, allowing the guide member 10to drop out of the enlarged side port 32 a. The deflatedcatheter/balloon assembly is then withdrawn, pulling the guide member 10along with it via the tether 18 and crimping lug 22 as shown in FIG. 8.After the catheter/balloon/guide loop assembly has been withdrawn, theside branch guidewire 52 may be reinserted through the tissue supportingdevice enlarged side hole 32 a and into the branch lumen 62 forsubsequent procedures.

The orientation accuracy of the delivery system can be improved by theaddition of one or more auxiliary guide loops to the guide member asillustrated in FIGS. 9 and 10. The guide member 70 as shown in FIG. 9includes the main loop 14 with the spacer section 16 and tabs 18, and anauxiliary loop 72. The auxiliary loop 72 is also provided with tabs 74which conform generally to the inner radius of the unexpanded tissuesupporting device in which the guide loop will be mounted. The auxiliaryloop 72 is connected the main loop. 14 by a first tether 76 and isconnected to the crimping lug 22 by a second tether 78. As shown in FIG.10, the auxiliary loop 72 extends through a second side port feature 80in the tissue supporting device 30. The additional one or more auxiliaryloops 72 are located proximal to the primary guide loop 14. Theinstallation procedure for the tissue supporting device 30 using theguide member 70 shown in FIGS. 9 and 10 would be performed in the samemanner as discussed above with respect to the embodiment employing asingle guide loop, however, the side branch guidewire 52 extends throughboth the main guide loop 14 and the auxiliary loop 72.

One common procedure to follow implantation of the tissue supportingdevice 30 into the main lumen would be implantation of a second tissuesupporting device in the branch lumen 62. A procedure very similar tothe one just outlined could be used to accomplish this task, by simplyreversing the roles of the main lumen and branch lumen guidewires. Asabove, a guide member is inserted into the side port of a second tissuesupporting device, and the assembly is crimped down on a conventionalcatheter balloon. In this case, the catheter and tissue supportingdevice assembly is mounted on the side branch guidewire 52, and the mainartery guidewire 50 is threaded through the guide member. As before, theentire assembly is fed to the bifurcation site, where the clevis formedby the tissue supporting device and main artery guidewire 50 comes torest against the distal side of the branch lumen opening. In this case,the side-port border-struts of the previously implanted tissuesupporting device 30 are also in place to provide an even more accuratestop for aligning the side hole edge of the incoming tissue supportingdevice at the distal side of the bifurcation.

The tissue supporting device deployment sequence for deploying thesecond device would now proceed as before: the distal end of the branchtissue supporting device would be expanded in the branch artery,anchoring the tissue supporting device in position, and the main arteryguidewire 50 would be retracted below the proximal end of the catheterballoon. The unexpanded proximal end of the second tissue supportingdevice now extends back into the main artery, with the tissue supportingdevice side port facing downstream in the main artery.

When expansion of the second tissue supporting device is completed, theproximal end of the second tissue supporting device will be implanted inthe main artery, with the second tissue supporting device bent aroundthe proximal side of the branch artery orifice. The side port of thesecond tissue supporting device will open exactly opposite this bend,since the leading edge of the side port was initially located at thebifurcation junction as described above. The side port thus opens topermit flow through the main artery, and the tissue supporting devicestruts arrayed opposite the side port provide support to the proximalside of the branch artery orifice (the bend area). After implantationhas been completed, the catheter/balloon/guide loop assembly iswithdrawn, completing the procedure.

Although the invention has been described with respect to providingsupport for bifurcated lumens in arteries, it should be understood thatthe invention may also be used to provide support for bifurcations inother bodily lumens.

While the invention has been described in detail with reference to thepreferred embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made and equivalentsemployed, without departing from the present invention.

1-22. (cancelled)
 23. A method for delivering an expandable medicaldevice to a vessel lumen, the method comprising: providing an expandablemedical device on a balloon catheter with the expandable medical devicehaving a distal end and a proximal end; delivering the expandablemedical device to the vessel lumen; expanding the distal end of theexpandable medical device by inflating the balloon catheter with a firstpressure; and expanding the proximal end of the expandable medicaldevice by inflating the balloon catheter with a second pressure higherthan the first pressure.
 24. The method of claim 23, wherein the vessellumen is a bifurcated vessel lumen.
 25. The method of claim 24, furthercomprising the steps of inserting a guidewire into a branch vessel ofthe bifurcated vessel, and removing the guidewire from the branch vesselafter the expansion of the distal end of the expandable medical deviceand before the expansion of the proximal end of the expandable medicaldevice.
 26. The method of claim 23, further comprising removing aguidewire from the vessel after the expansion of the distal end of theexpandable medical device and before the expansion of the proximal endof the expandable medical device.
 27. The method of claim 23, whereinthe expandable medical device distal end is configured to expand at thefirst pressure and the expandable medical device distal end isconfigured to expand at the second pressure by varying the structure ofthe expandable medical device struts.
 28. The method of claim 23,wherein the expandable medical device is formed with a plurality ofstuts interconnected by ductile hinges, and wherein the ductile hingeshape differs between the distal and proximal ends of the device. 29.The method of claim 23, wherein the expandable medical device isexpandable to a device having a plurality of struts, a plurality ofspaces between the struts, and a side hole for accommodating abifurcation which is larger than the spaces between the struts.
 30. Themethod of claim 29, wherein the distal end which expands first islocated distally of the side hole and the proximal end which expandssecond is located proximally of the side hole.
 31. A system for placingan expandable medical device in a bifurcated body lumen, the systemcomprising: a balloon catheter having a balloon and a catheter shaft;and an expandable medical device mounted on the balloon, the expandablemedical device having an expandable structure, a distal end, and aproximal end, wherein the distal end is configured to expand at a firstpressure and the second end is configured to expand at a second pressurehigher than the first pressure.
 32. The system of claim 31, wherein theexpandable medical device is formed with a plurality of stutsinterconnected by ductile hinges, and wherein the ductile hinge shapediffers between the distal and proximal ends of the device.
 33. Thesystem of claim 32, wherein the ductile hinges in the distal end havewidths smaller than the ductile hinges in the proximal end.
 34. Thesystem of claim 31, wherein the expandable medical device is expandableto form a lumen supporting device having a plurality of struts, aplurality of spaces between the struts, and a side hole foraccommodating a bifurcation which is larger than the spaces between thestruts.